The present invention relates to an electric laundry washing machine, particularly for domestic use, wherein a wash liquor or washing liquid is caused to recirculate through the wash tub to wet the laundry therein to carry out a washing operation with considerable savings in use of water, detergent and energy.
A laundry washing machine of this general principle would also adapt to perform the traditional washing cycles by soaking the laundry as described in European Patent Application No. 0,146,719. Such washing machine includes a wash tub with a basket receiving laundry and mounted for rotation within the wash tub, and a container or sump is connected to the lower portion or bottom of the wash tub and collects therefrom the washing liquid which is to be recirculated back to an upper portion of the wash tub. Within the container or sump are located electrical resistor heaters for heating the washing liquid. A pump then withdraws the thus heated washing liquid from the container or sump and passes it through a conduit or duct that leads into the upper portion of the wash tub to thereby discharge the heated washing liquid into the wash tub to wet the laundry within the perforated basket spinning within the wash tub.
This known washing machine, although functionally correct, can be improved structurally with regard to the hydraulic circuit thereof, and also can be supplemented conveniently with a drying circuit so as to provide for a more complete processing of the laundry. Indeed, the positioning of the container or sump for collection of the washing liquid in the lower part of the machine results in assembly problems, given the necessary limited space available due to the small and standardized dimensions of domestic washing machines. Furthermore, filtering devices and controls are necessary in order to prevent lint and mineral deposits that are damaging to the electrical resistor heaters from being accumulated in the container or sump. Accordingly, it would preferably to position the collecting container or sump at the upper part of the washing machine. Indeed, a solution of this general type was proposed in 1910 in German Pat. No. 234,908. However, in such known arrangement, the container or tank for collecting and heating the washing liquid is provided externally of the washing machine, and the washing liquid passes therethrough from top to bottom, reentering the tub through a hollow shaft of the basket.
In addition to the complex and bulky construction of this machine, which indeed is not feasible with regard to domestic washing machines, this arrangement has additional inherent and serious disadvantages. Indeed, a heavy consumption of energy is necessary in order to sufficiently heat the water flowing continuously through the collecting container or tank, unless closure valves are provided between the collecting tank and the wash tub. Furthermore, the hydraulic pressure losses along the connecting pipes between the collecting tank and the wash tub reduce substantially the efficiency of the jets of washing liquid issuing from sprinklers disposed along the jacket of the basket containing the laundry. Finally, this known machine does not provide any capability of drying the laundry.
More recently, there have become known machines of the combined washing and drying type wherein laundry is not only washed, but also is dried. However, in such known machines, washing is effected in a traditional manner with the soaking of the clothes, and the washing and drying circuits usually are separated, except for the possible use of water from the water supply main also being employed for condensing water vapor resulting from the drying operation. Hence, machines of this type are complex structurally and are not economical from an operational point of view. One such machine is disclosed in U.S. Pat. No. 4,154,003. The recent development of recirculation-type laundry washing machines, in which heating elements are disposed externally of the wash tub, affords the possibility of the advantageous construction of a combined appliance for washing and drying of laundry.